Dental caries remains among the most prevalent infectious diseases worldwide. Over 84 percent of U.S. children, 96 percent of U.S. adults, and 99.5 percent of Americans 65 years of age and older have experienced tooth decay. To conceptualize and develop novel anticaries strategies that can be effectively distributed to the population, a molecular dissection of the genetics, physiology and biochemistry of cariogenic microorganisms is needed. Our work during the previous funding period has led to the discovery of novel and unique mechanisms for the control of the degradation of dental plaque polysaccharides and revealed important connections between the amount of carbohydrates available to cells and the capacity of these cells to express essential virulence determinants, including the capacity to produce exo-polysaccharides and to tolerate acidic conditions. Further, our work has led to the discovery that global regulators of carbohydrate metabolism play essential roles in regulation of virulence and expression of acid tolerance. The major goals of this application are to continue with our fundamental studies on gene regulation and physiology of S. mutans, with a particular focus on the control of virulence gene expression by carbohydrate availability, pH and the global control protein CcpA. To accomplish these goals, we have established the following four Specific Aims. 1. A detailed analysis of a transcriptional activator required for fructanase (fruA) expression and analysis of the molecular basis for PTS-mediated control of expression of fructan degradation. 2. Identification of the protein(s) that interacts with the fruA catabolite response elements. 3. Molecular dissection of the basis for the control of exo-polysaccharide production by carbohydrate availability and CcpA. 4. Physiologic and genetic analysis of the linkage between limitation for carbohydrate, the CcpA regulon and control of virulence gene expression. These studies combine sophisticated molecular genetic tools with powerful physiologic techniques to dissect the pathways used by S. mutans to alter its pathogenic potential in response to carbohydrate availability. Understanding these pathway will allow for the design of technologies that subvert the capacity of S. mutans to become a numerically significant constituent of a cariogenic microflora.